In machines, devices and systems which operate under vacuum or fluid pressure, such as pneumatic cylinders and the like, it is important that performance is optimal and that fluid leakage from the components be minimized if not eliminated altogether. In an effort to ensure optimum performance, the components of these systems frequently are subjected to rigorous and exacting testing procedures to determine if leaks exist in the system components by measuring their ability to maintain their desired pressure or vacuum over a period of time.
In the past it was common for manufacturers of such systems and their components to perform pressure or vacuum tests on the components during production and prior to assembly of the components into the system by utilizing fluid operated test devices for identifying components, such as pneumatic cylinders, that do not measure up to the necessary leak integrity requirements. These prior art test devices generally have included a cylinder having a cylindrical resilient sleeve adjacent an end of the cylinder. The sleeve was formed of an elastomer, such as neoprene or urethane. A piston in the cylinder and a rod on the piston extends through an end of the cylinder and the resilient sleeve is mounted on the end of the rod. The rod included an abutment on its end for trapping the resilient sleeve between one end of the cylinder and the abutment to compress it when fluid pressure was introduced into the cylinder of the test device. This caused the cylindrical sleeve to expand into the port of the component being tested. Once the port was sealed, a pressurized fluid was then introduced through the rod to pressurize the component being tested. Various pressure indicating devices attached to the fluid supply could then be monitored to insure that the component pressure over time was within established standards or parameters.
Because even the slightest leak through the port of the component being tested can significantly alter and detract from the test results, it is imperative that the sleeve connection in the port of the component in which it is inserted is leak tight. One problem associated with the prior art cylindrical sleeve test devices, particularly when employed to test components with internally threaded test ports, was the short life span of the resilient sleeve if sufficient compression was applied to the sleeve to insure a fluid tight seal. In order to achieve a seal in the test devices utilizing a cylindrical sleeve, the cylindrical sleeve must radially expand during its axial compression so as to fully and deeply enter the roots of the threads of the port. As a result if these test devices are to be leak proof, the resilient sleeve frequently was damaged by the threads, thus significantly decreasing the number of times a test device could be used before its sleeve became ineffective. On the otherhand if the degree of compression is reduced in the interest of longevity of the resilient sleeve, undesirable leaks occurred through the port threads which reduced the reliability of the prior test devices.
In an effort to remedy this problem, some prior art test devices have also utilized a second and separate annular resilient seal to bear against the end face around the port of the component being tested. This seal sealed the face of the component in conjunction with the radially expanding cylindrical resilient sleeve. Such second seal permitted the prior test devices to be operated at somewhat lower pressures so that the cylindrical sleeve need only be compressed and expanded to a lesser degree and depth into the roots of the port threads and, thereby, permitted increased longevity of the sleeve. However, the provision of this second separate seal results in increased costs, additional assembly time and increased inventory requirements for the separate parts. Additionally, the effectiveness of these two part seals is substantially reduced where the face of the cylinder containing the port is rounded or has a contour other than substantially flat because the second seal cannot fully seat against such contour.